Comment #5 on issue 2864 by [email protected]: Parsing issue with
mathematica.py with regex expressions
http://code.google.com/p/sympy/issues/detail?id=2864
You can use regexes for bottom-up parsing:
a) Use a token-to-subtree dict.
b) Write a regex that recognizes only innermost expressions (i.e. those
that do not contain parentheses themselves). Build the bottom nodes as with
normal regex-based parsing.
c) In the input string, replace the recognized strings with tokens that
aren't in the string. Enter the recognized strings in the dict, with the
token as key.
d) Repeat from b until the whole string is recognized.
e) Use the dict to build the parse tree.
It's not pretty, it's not efficient, but it's straightforward and a gradual
route from regex parsing.
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